This disclosure relates to substrate processing, and, more particularly, to techniques for patterning substrates including patterning of semiconductor wafers.
Methods of shrinking line-widths in lithographic processes have historically involved using greater-NA (numerical aperture) optics, shorter exposure wavelengths, or interfacial media other than air (e.g., water immersion). As the resolution of traditional lithographic processes has approached theoretical limits, manufacturers have started to turn to double-patterning (DP) methods to overcome optical limitations.
In material processing methodologies (such as photolithography), creating patterned layers comprises the application of a thin layer of radiation-sensitive material (such as photoresist) to a surface of a substrate. This radiation-sensitive material is transformed into a relief pattern (patterned mask) that can be used to etch or transfer a pattern into an underlying layer on a substrate. Patterning of the radiation-sensitive material generally involves exposure by a radiation source through a reticle (and associated optics) onto the radiation-sensitive material using, for example, a photolithography system. This exposure can then be followed by the removal of irradiated regions of the radiation-sensitive material (as in the case of positive photoresist), or non-irradiated regions (as in the case of negative resist) using a developing solvent. This patterned mask may comprise multiple sub-layers.